U.S. patent application number 13/640992 was filed with the patent office on 2013-04-25 for planetary gear system.
This patent application is currently assigned to KAWASAKI JUKOGYO KABUSHIKI KAISHA. The applicant listed for this patent is Hidenori Arisawa, Tatsuhiko Goi, Hideyuki Imai, Motohiko Nishimura, Maiko Sato. Invention is credited to Hidenori Arisawa, Tatsuhiko Goi, Hideyuki Imai, Motohiko Nishimura, Maiko Sato.
Application Number | 20130102432 13/640992 |
Document ID | / |
Family ID | 44798463 |
Filed Date | 2013-04-25 |
United States Patent
Application |
20130102432 |
Kind Code |
A1 |
Imai; Hideyuki ; et
al. |
April 25, 2013 |
PLANETARY GEAR SYSTEM
Abstract
A planetary gear system (1) includes: a sun gear (5) having
external teeth; a plurality of planet gears (7) having external
teeth, each planet gear meshing with the sun gear; a ring gear (9)
having internal teeth, the ring gear meshing with the planet gears;
and a baffle unit (35) disposed between the planet gears which are
adjacent to each other, the baffle unit having side faces (37F,
37R) positioned near the respective planet gears. The baffle unit
(35) has: oil supply holes (47) which are formed in a tip portion
(41) facing an outer periphery of the sun gear (5) and which jet
out lubricating oil (OL) to mesh positions (43, 45) between the sun
gear and the planet gears; and a collection opening (55) which is
formed in at least one of the side faces and through which the
lubricating oil (OL) that has been jetted out is collected into the
baffle unit (35).
Inventors: |
Imai; Hideyuki; (Akashi-shi,
JP) ; Goi; Tatsuhiko; (Kobe-shi, JP) ;
Arisawa; Hidenori; (Kakogawa-shi, JP) ; Nishimura;
Motohiko; (Matsudo-shi, JP) ; Sato; Maiko;
(Kobe-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Imai; Hideyuki
Goi; Tatsuhiko
Arisawa; Hidenori
Nishimura; Motohiko
Sato; Maiko |
Akashi-shi
Kobe-shi
Kakogawa-shi
Matsudo-shi
Kobe-shi |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
KAWASAKI JUKOGYO KABUSHIKI
KAISHA
Kobe-shi, Hyogo
JP
|
Family ID: |
44798463 |
Appl. No.: |
13/640992 |
Filed: |
April 8, 2011 |
PCT Filed: |
April 8, 2011 |
PCT NO: |
PCT/JP2011/002082 |
371 Date: |
December 21, 2012 |
Current U.S.
Class: |
475/159 |
Current CPC
Class: |
F05D 2260/40311
20130101; F05D 2260/98 20130101; F16H 57/0409 20130101; F16H
57/0427 20130101; F16H 57/045 20130101; F16H 57/0486 20130101; F02C
7/36 20130101; F16H 57/042 20130101; F16H 57/0479 20130101; F16H
57/082 20130101 |
Class at
Publication: |
475/159 |
International
Class: |
F16H 57/04 20060101
F16H057/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2010 |
JP |
2010-092559 |
Claims
1. A planetary gear system comprising: a sun gear having external
teeth; a plurality of planet gears having external teeth, each
planet gear meshing with the sun gear; a ring gear having internal
teeth, the ring gear meshing with the planet gears; and a baffle
unit disposed between the planet gears which are adjacent to each
other, the baffle unit having side faces positioned near outer
peripheries of the respective planet gears, wherein the baffle unit
has: oil supply holes which are formed in a tip portion facing an
outer periphery of the sun gear and which jet out lubricating oil
to mesh positions between the sun gear and the planet gears; and a
collection opening which is formed in at least one of the side
faces and through which the lubricating oil that has been jetted
out is collected into the baffle unit.
2. The planetary gear system according to claim 1, wherein each
planet gear is a double helical gear having an annular groove
formed at an outer circumferential face of an axially central
portion of the double helical gear.
3. The planetary gear system according to claim 1, wherein a guide
piece which guides the lubricating oil to the collection opening is
formed at the at least one of the side faces of the baffle
unit.
4. The planetary gear system according to claim 1, wherein the
baffle unit has a ring gear oil supply hole formed therein, through
which the collected lubricating oil is supplied to the ring
gear.
5. The planetary gear system according to claim 1, wherein the
baffle unit has an outlet formed therein, through which the
collected lubricating oil is discharged in an axial direction.
6. The planetary gear system according to claim 5, wherein the
baffle unit includes a weir, which blocks the outlet at a radially
outer side of the planet gears and at a backward side with respect
to a revolution direction of the planet gears.
7. The planetary gear system according to claim 1, wherein a
collection guide groove which guides the lubricating oil to the
collection opening is formed so as to extend from an inner end of
the at least one of the side faces of the baffle unit to the
collection opening.
Description
TECHNICAL FIELD
[0001] The present invention relates to a planetary gear system
mainly used in a power transmission mechanism of an aircraft, and
particularly to a lubricating structure of such a planetary gear
system.
BACKGROUND ART
[0002] In recent years, one of the key issues in the aircraft
industry is to improve the fuel efficiency of aircrafts from the
viewpoint of reduction of aircraft operation costs as well as
environmental conservation. Accordingly, reduction in power loss of
planetary gear systems for use in aircraft engines is also
required.
[0003] Conventionally, such a planetary gear system includes a
mechanism for supplying lubricating oil to the gears for the
purpose of lubricating and cooling down the gears. Here, agitation
resistance of the lubricating oil that is supplied around the gears
is one of the main causes of power loss in the planetary gear
system. One of the techniques proposed for reducing such agitation
resistance of lubricating oil is, for example, as follows:
lubricating oil that has been supplied to a mesh position between a
sun gear and a planet gear is discharged axially by utilizing
rotation of the planet gear which is a double helical gear, and a
baffle (a barrier) is provided between adjacent planet gears, so
that generation of a swirl flow due to interference of flows of
lubricating oil that are generated around the adjacent planet gears
is suppressed (see Patent Literature 1, for example).
CITATION LIST
Patent Literature
[0004] PTL 1: Japanese National Phase PCT Laid-Open Publication No.
9-507284
SUMMARY OF INVENTION
Technical Problem
[0005] However, in relation to the above structure, there is a
conceivable problem as described below. In the above structure, the
lubricating oil which is a fluid is discharged from the axially
central portion of the double helical gear in both outward
directions. Here, no locally vacuum portion occurs in the fluid.
Considering such continuity of the fluid, it is presumed that
efficient discharging of the lubricating oil is difficult.
Moreover, since a baffle is disposed near the outer periphery of a
planet gear, the lubricating oil that exits the mesh position flows
out while being adhered to the outer periphery of the planet gear.
As a result, the agitation resistance of the lubricating oil
increases.
[0006] Furthermore, it is difficult to reduce power loss
sufficiently unless not only lubricating oil around the central sun
gear and planet gears but also lubricating oil around other
rotating components, such as an outer peripheral ring gear and
bearings provided in the planetary gear system, are smoothly
discharged.
[0007] An object of the present invention is to provide a planetary
gear system with reduced power loss, by reducing lubricating oil
agitation resistance through efficient discharging of lubricating
oil supplied to main rotating components of the planetary gear
system.
Solution to Problem
[0008] In order to achieve the above object, a planetary gear
system according to the present invention includes: a sun gear
having external teeth; a plurality of planet gears having external
teeth, each planet gear meshing with the sun gear; a ring gear
having internal teeth, the ring gear meshing with the planet gears;
and a baffle unit disposed between the planet gears which are
adjacent to each other, the baffle unit having side faces
positioned near outer peripheries of the respective planet gears.
The baffle unit has: oil supply holes which are formed in a tip
portion facing an outer periphery of the sun gear and which jet out
lubricating oil to mesh positions between the sun gear and the
planet gears; and a collection opening which is formed in at least
one of the side faces and through which the lubricating oil that
has been jetted out is collected into the baffle unit.
[0009] According to this structure, the baffle unit is provided
between the planet gears which are adjacent to each other, and the
baffle unit collects the lubricating oil therein while preventing
flows of the lubricating oil around the respective adjacent planet
gears from interfering with each other. This makes it possible to
prevent a large amount of lubricating oil from being adhered to the
outer periphery of the planet gears over a long circumferential
distance. Accordingly, the agitation resistance of the lubricating
oil is reduced. As a result, power loss of the planetary gear
system is reduced.
[0010] In the planetary gear system according to the present
invention, each planet gear is preferably a double helical gear
having an annular groove formed at an outer circumferential face of
an axially central portion of the double helical gear. According to
this structure, the lubricating oil can be collected into the
annular groove of the axially central portion of each planet gear
by utilizing rotation of the planet gear. This makes it possible to
efficiently discharge the lubricating oil.
[0011] In the planetary gear system according to the present
invention, it is preferred that a guide piece which guides the
lubricating oil to the collection opening is formed at the at least
one of the side faces of the baffle unit. According to this
structure, the amount of lubricating oil that flows outward in the
planetary gear system beyond the collection opening can be reduced.
Therefore, the lubricating oil can be very efficiently collected
into the baffle unit through the collection opening.
[0012] In the planetary gear system according to the present
invention, it is preferred that the baffle unit has a ring gear oil
supply hole formed therein, through which the collected lubricating
oil is supplied to the ring gear. According to this structure, the
lubricating oil that has been collected into the baffle unit can be
discharged to the radially outer side of the planetary gear system,
and also, the lubricating oil can be used to lubricate the ring
gear. This makes it possible to effectively reduce power loss of
the planetary gear system.
[0013] In the planetary gear system according to the present
invention, it is preferred that the baffle unit has an outlet
formed therein, through which the collected lubricating oil is
discharged in an axial direction. According to this structure, the
collected lubricating oil is discharged in the axial direction, and
thereby the collection of the lubricating oil can be facilitated.
Therefore, the agitation resistance can be reduced more
effectively.
[0014] In the planetary gear system according to the present
invention, the baffle unit may include a weir, which blocks the
outlet at a radially outer side of the planet gears and at a
backward side with respect to a revolution direction of the planet
gears. Since the weir is provided at the outlet as described above,
a sufficient amount of lubricating oil to be supplied to the ring
gear through the ring gear oil supply hole can be kept within the
baffle unit. In particular, Centrifugal force and Coriolis force
generated by revolution of the planet gears are both exerted on the
lubricating oil that has been collected into the baffle unit.
Accordingly, the lubricating oil can be effectively kept by
blocking, with the weir, the outlet at the radially outer side of
the planet gears and at the backward side with respect to the
revolution direction of the planet gears, that is, by blocking,
with the weir, a portion positioned in the direction of resultant
force of the centrifugal force and the Coriolis force.
[0015] In the planetary gear system according to the present
invention, it is preferred that a collection guide groove which
guides the lubricating oil to the collection opening is formed so
as to extend from an inner end of the at least one of the side
faces of the baffle unit to the collection opening. According to
this structure, the lubricating oil can be collected more
effectively.
Advantageous Effects of Invention
[0016] According to the planetary gear system of the present
invention, lubricating oil supplied to main rotating components of
the planetary gear system can be efficiently discharged. As a
result, the agitation resistance of the lubricating oil is reduced,
and thereby power loss of the planetary gear system is reduced
greatly.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a partially cutaway perspective view showing a
planetary gear system according to one embodiment of the present
invention.
[0018] FIG. 2 is a longitudinal sectional view of the planetary
gear system shown in FIG. 1.
[0019] FIG. 3 is a transverse sectional view of the planetary gear
system shown in FIG. 1.
[0020] FIG. 4 is a cross-sectional view along line IV-IV indicated
in FIG. 3.
[0021] FIG. 5 is a perspective view of baffle units shown in FIG.
3.
[0022] FIG. 6 is a cross-sectional view of a variation of the
planetary gear system shown in FIG. 3.
[0023] FIG. 7 is a cross-sectional view showing a main part of FIG.
3 in an enlarged manner.
[0024] FIG. 8 is a front view of a planet gear for use in the
planetary gear system shown in FIG. 1.
[0025] FIG. 9 is a transverse sectional view of a ring gear for use
in the planetary gear system shown in FIG. 1.
DESCRIPTION OF EMBODIMENTS
[0026] Hereinafter, a preferred embodiment of the present invention
is described with reference to the accompanying drawings. FIG. 1 is
a perspective view showing a planetary gear system 1 according to
one embodiment of the present invention. The planetary gear system
1 is installed in an aircraft engine, and transmits power of an
input shaft 3 as two outputs. It should be noted that in the
description below, along the axial direction of the planetary gear
system 1, one side of the planetary gear system 1, at which side
the engine is disposed (i.e., the lower left side in FIG. 1), is
referred to as a front side, and the opposite side is referred to
as a rear side.
[0027] The planetary gear system 1 is configured as a double-row
gear mechanism, which includes: a central sun gear 5; planet gears
7; and an outer ring gear 9. The sun gear 5 is a double helical
gear including a pair of helical gears and having sets of external
teeth, the sets of external teeth being inclined in respective
directions that are opposite to each other. The sun gear 5 is
fitted to the outer periphery of the input shaft 3 which acts as
the rotational axis. Each planet gear 7 is a double helical gear
having a pair of sets of external teeth, and includes helical gears
corresponding to the helical gears of the sun gear 5. Each planet
gear 7 meshes with the sun gear 5. As described in detail below in
this embodiment, four planet gears 7 are arranged in the
circumferential direction of the sun gear 5 at equal intervals. The
ring gear 9 is a double helical gear including a pair of helical
gears with internal teeth. The ring gear 9 meshes with the four
planet gears 7. The sun gear 5 has an annular groove 16 formed at
its axially central portion, that is, at its outer circumferential
face between the pair of sets of teeth. Also, each planet gear 7
has an annular groove 17 formed at its axially central portion,
that is, at its outer circumferential face between the pair of sets
of teeth. Further, the ring gear 9 has an annular groove 18 formed
at its axially central portion, that is, at its inner
circumferential face between the pair of sets of teeth. FIG. 2 is a
longitudinal sectional view showing a main part of the planetary
gear system 1 in FIG. 1. In FIG. 2, the front side is on the left,
and the rear side is on the right. As shown in FIG. 2, each planet
gear 7 is rotatably supported, via a respective double row bearing
15, at the outer periphery of a corresponding planet shaft 13 which
has a hollow center. Both front and rear ends of the planet shaft
13 are attached to a planet carrier 11.
[0028] The front end of the planet shaft 13 is supported by an
annular front plate 19 which shares the same central axis C1 with
the input shaft 3. On the other hand, the rear end of the planet
shaft 13 is supported by an annular back plate 21 which is disposed
concentrically to the front plate 19. As described in detail below,
the back plate 21 is connected and fixed to the front plate 19 via
fixed support shafts 23. The front plate 19 and the back plate 21,
which are connected to each other by bolts via the fixed support
shafts 23, form the planet carrier 11 which supports the planet
shafts 13 and the planet gears 7. The planet carrier 11 determines
the relative positions of the planet shafts 13 relative to one
another, that is, determines the relative positions of the planet
gears 7 relative to one another.
[0029] The front end of each planet shaft 13 in the axial direction
penetrates through the front plate 19, and the rear end of each
planet shaft 13 in the axial direction penetrates through the back
plate 21. The front plate 19 is fixed to the front end of each
planet shaft 13 in the axial direction by means of the respective
fixed support shaft 23, which is a headed shaft having a hollow
center and which is inserted in the hollow center of the
corresponding planet shaft 13 through the front end of the planet
shaft 13. The back plate 21 is fixed to the rear end of each planet
shaft 13 in the axial direction by means of a respective headed nut
threadably mounted to a female screw provided at the rear end of
the corresponding planet shaft 13. In this manner, the front plate
19, the planet shafts 13, and the back plate 21 are fastened in the
axial direction and thereby fixed. For each planet shaft 13,
cushioning 28 and a spacer 29 are interposed between the outer
periphery of the planet shaft 13 and the front plate 19, as well as
between the outer periphery of the planet shaft 13 and the back
plate 21.
[0030] A front output shaft OF, which is concentric to the input
shaft 3, is connected to the outer circumferential face of the
front plate 19. Power derived from revolution of the four planet
gears 7 around the system's central axis C1 is outputted frontward
via the front output shaft OF. A rear output shaft OR, which is
concentric to the input shaft 3, is connected to the rear side of
the outer periphery of the ring gear 9. Power derived from rotation
of each planet gear 7 around its rotational central axis C2 is
outputted rearward via the ring gear 9 and the rear output shaft
OR. It should be noted that, as an alternative, the ring gear 9 may
be set to be not rotatable or the planet carrier 11 may be set to
be not rotatable, such that the power is outputted either frontward
only or rearward only.
[0031] FIG. 3 shows a transverse sectional view of the planetary
gear system 1 along line III-III indicated in FIG. 2. The four
planet gears 7 are arranged in the circumferential direction at
equal intervals between the sun gear 5 and the ring gear 9. There
are multiple intergear spaces 33 (in this embodiment, four
intergear spaces 33 in total), each of which is surrounded by the
sun gear 5, two planet gears 7 that are adjacent to each other in
the circumferential direction, and the ring gear 9. A baffle unit
35 is provided in each intergear space 33. Hereinafter, the
structure of the baffle unit 35 is described in detail. It should
be noted that, when one among the baffle units 35 is referred to in
the description below, the planet gear 7 that is positioned forward
from the one baffle unit 35 with respect to the counterclockwise
revolution direction Rv of the planet gears 7 may be called a
"forward planet gear 7F", and the planet gear 7 that is positioned
backward from the one baffle unit 35 with respect to the revolution
direction Rv may be called a "backward planet gear 7R".
[0032] Each baffle unit 35 includes an inner portion 35a and an
outer portion 35b. The inner portion 35a is positioned at the
radially inner part of the intergear space 33, which is a part
close to the system's central axis C1. The outer portion 35b is
positioned at the radially outer part of the intergear space 33,
which is a part close to the ring gear 9. In the diagram, the inner
portion 35a is indicated by dashed-line hatching, and the outer
portion 35b is indicated by solid-line hatching.
[0033] As shown in FIG. 3, the baffle unit 35 has a forward side
face 37F which is formed in a recessed curved shape. The forward
side face 37F has a part that extends substantially along the outer
circumferential shape of the forward planet gear 7F, the part
extending from the inner portion 35a to the inner part of the outer
portion 35b. The forward side face 37F of the baffle unit 35 is
positioned near the forward planet gear 7F. A forward gap 38 having
a curved transverse sectional shape is formed between the forward
side face 37F of the baffle unit 35 and the forward planet gear 7F.
Similarly, the inner portion 35a of the baffle unit 35 has a
backward side face 37R which is formed in a recessed curved shape
and which extends substantially along the outer circumferential
shape of the backward planet gear 7R. The backward side face 37R of
the baffle unit 35 is positioned near the backward planet gear 7R.
A backward gap 39 having a curved transverse sectional shape is
formed between the backward side face 37R of the baffle unit 35 and
the backward planet gear 7R.
[0034] The baffle unit 35 has a tip portion 41 which faces the
outer periphery of the sun gear 5. The tip portion 41 has a tip
face 41a which is positioned near the sun gear 5 and which has a
curved shape substantially extending along the outer periphery of
the sun gear 5. The tip face 41a of the baffle unit 35 is
positioned near the sun gear 5. An inner gap 42 having a curved
transverse sectional shape is formed between the tip face 41a of
the baffle unit 35 and the sun gear 5. A forward inclined face 41b
is formed at one end of the tip face 41a of the baffle unit 35 and
a backward inclined face 41c is formed at the other end of the tip
face 41a of the baffle unit 35. The forward inclined face 41b faces
a mesh position 43 between the sun gear 5 and the forward planet
gear 7F (forward mesh position). The backward inclined face 41c
faces a mesh position 45 between the sun gear 5 and the backward
planet gear 7R (backward mesh position).
[0035] Preferably, the size of each of the forward gap 38, the
backward gap 39, and the inner gap 42 is in the range of 3 to 7 mm.
More preferably, the size of each gap is in the range of 4 to 6 mm.
Setting the size of each gap within this range makes it possible to
suppress an increase in the overall size of the planetary gear
system 1 and to sufficiently obtain a path for lubricating oil OL
that has not flowed into any of the annular grooves 16, 17, and 18
of the sun gear 5, the planet gears 7, and the ring gear 9 (see
FIG. 1) and that remains on the tooth surface of these gears. This
contributes to reducing the agitation resistance of the lubricating
oil OL.
[0036] FIG. 4 is a cross-sectional view along line IV-IV indicated
in FIG. 3. In FIG. 4, the front side is on the left, and the rear
side is on the right. As shown in FIG. 4, the inner portion 35a of
the baffle unit 35 is formed as a solid portion, and is fixed to
the back plate 21 by bolts 49. The front plate 19 and the back
plate 21 are connected to each other by a bolt 51. A gear
lubricating oil guide path 53A is formed at the inner portion 35a
of the baffle unit 35. A gear lubricating oil guide path 53B is
formed at the front plate 19. These gear lubricating oil guide
paths 53A and 53B communicate with oil supply holes 47 which will
be described below. At the inner circumferential portion of the
front plate 19, a cylindrical portion 19a is formed to protrude
frontward in the axial direction. The gear lubricating oil guide
path 53B communicates with the outside via the outer
circumferential face of the cylindrical portion 19a.
[0037] As shown in FIG. 5, the forward inclined face 41b and the
backward inclined face 41c of the baffle unit 35 are each provided
with multiple oil supply holes 47 (in this embodiment, six oil
supply holes 47) which are arranged in the axial direction. The oil
supply holes 47 are provided for jetting out the lubricating oil OL
which is supplied from the outside.
[0038] A backward collection opening 55 is formed in the backward
side face 37R of the baffle unit 35, such that the backward
collection opening 55 is located at a position near the boundary
between the inner portion 35a and the outer portion 35b, which
position is substantially the central position of the backward side
face 37R in the axial direction. The backward collection opening 55
is provided for collecting the jetted lubricating oil OL into the
baffle unit 35. The backward collection opening 55 is open in the
inner radial direction of the planetary gear system 1. A collection
guide groove 57 for guiding the lubricating oil OL to the backward
collection opening 55 is formed so as to extend from the inner end
of the backward side face 37R to the backward collection opening
55. The collection guide groove 57 has an axial direction width W,
which is greatest at the inner end of the backward side face 37R.
The shorter the distance to the backward collection opening 55,
which is located outer than the inner end of the backward side face
37R, the smaller is the axial direction width W.
[0039] The collection guide groove 57 has a central portion 57a
which is formed as a deeper groove than its adjacent portions. The
central portion 57a is the central portion of the collection guide
groove 57 in the axial direction, and its position in the axial
direction corresponds to that of the annular groove 17 (FIG. 2) of
the planet gear 7. It should be noted that the multiple oil supply
holes 47 are not formed at axial directional positions that
correspond to the position, in the axial direction, of the central
portion 57a of the collection guide groove 57, but are formed at
equal intervals at more frontward and rearward positions in the
axial direction. That is, the multiple oil supply holes 47 are
formed such that their positions in the axial direction correspond
to the positions of the teeth of the planet gear 7 and the teeth of
the sun gear 5 in the axial direction (FIG. 2).
[0040] Further, as shown in FIG. 5, ring gear oil supply holes 59,
which are through-holes extending in the radial direction, are
formed in a wall 35c of the baffle unit 35. The wall 35c is the
outermost portion of the baffle unit 35. The ring gear oil supply
holes 59 (in this embodiment, two ring gear oil supply holes 59) in
the wall 35c are arranged in the axial direction with a
predetermined interval therebetween. The ring gear oil supply holes
59 are arranged at positions that are located backward from the
center of the wall 35c with respect to the revolution direction Rv
of the planet gear 7. It should be noted that the number and the
positions of the oil supply holes 47 and the ring gear oil supply
holes 59 may be set to any number and positions as
appropriately.
[0041] A forward collection opening 63 is formed in the forward
side face 37F of the baffle unit 35, such that the forward
collection opening 63 is located at the substantially central
position in the axial direction at the outer end of the forward
side face 37F, that is, near the boundary between the inner portion
35a and the outer portion 35b. The forward collection opening 63 is
provided for collecting the jetted lubricating oil OL into the
baffle unit 35. The forward collection opening 63 is open inward in
a direction diagonal to the radial direction of the planetary gear
system 1.
[0042] It should be noted that, as in a variation shown in FIG. 6,
a guide piece 61 may be provided at the outer side of the backward
collection opening 55. The guide piece 61 provided at the outer
side of the backward collection opening 55 is a claw-like member
which protrudes inward. The tip of the guide piece 61 is positioned
within the annular groove 17 which is formed at the center of the
planet gear 7. The guide piece 61 blocks the lubricating oil OL
from flowing outward beyond the backward collection opening 55, and
guides the lubricating oil OL into the backward collection opening
55. The guide piece 61 may be formed to be integrated with the
baffle unit 35. Alternatively, the guide piece 61 may be formed as
a separate component from the baffle unit 35, and then joined to
the baffle unit 35 by welding or the like.
[0043] As shown in FIG. 4, the outer portion 35b of the baffle unit
35 is formed to have a hollow center. The inner space of the baffle
unit 35 communicates with the backward collection opening 55 and
the forward collection opening 63, and acts as a collection chamber
65 which provisionally stores the lubricating oil OL that is
collected through these collection openings 55 and 63. An opening
of the collection chamber 65 at the rear end in the axial direction
is fully sealed by the back plate 21. Meanwhile, an opening of the
collection chamber 65 at the front end in the axial direction acts
an axial directional outlet 67 for discharging the lubricating oil
OL from the collection chamber 65 to the outside of the baffle unit
35 in the axial direction. The axial directional outlet 67 is
partially blocked by a weir 69.
[0044] As shown in FIG. 7 which is an enlarged view of a main part
of FIG. 3, the weir 69 blocks the radially outer side of the axial
directional outlet 67 and the backward side of the axial
directional outlet 67 with respect to the revolution direction Rv.
Centrifugal force Cf and Coriolis force Co generated by the
revolution of the planet gear 7 are both exerted on the lubricating
oil OL that is collected within the collection chamber 65 of the
baffle unit 35. Accordingly, the lubricating oil OL can be
effectively caught into the collection chamber 65 by blocking, with
the weir 69, the radially outer side of the axial directional
outlet 67 and the backward side of the axial directional outlet 67
with respect to the revolution direction Rv, that is, by blocking,
with the weir 69, a portion positioned in the direction of
resultant force Re of the centrifugal force Cf and the Coriolis
force Co. Moreover, since the ring gear oil supply holes 59 in the
wall 35c are arranged at positions that are located backward from
the center of the wall 35c with respect to the revolution direction
Rv of the planet gear 7, the lubricating oil OL is assuredly
supplied to the ring gear 9 through the ring gear oil supply holes
59.
[0045] Next, a lubricating structure of the bearing 15 and a
lubricating oil drainage structure are described with reference to
FIG. 2. The bearing 15, which is disposed between the planet gear 7
and the planet shaft 13, is formed as a double-row roller bearing
which includes two rolling element rows 72. Each rolling element
row 72 includes: multiple rolling elements 73 which are cylindrical
rollers; and an annular retainer 75 holding the rolling element row
72. The planet shaft 13 acts as an inner ring for the bearing 15.
For each rolling element row 72, a rolling surface 77 for the
rolling elements 73 is formed on the outer circumferential face of
the planet shaft 13. Further, annular flanges 79 for restricting
the position of the rolling elements 73 in the axial direction are
provided at both ends of each rolling surface 77 in the axial
direction.
[0046] In the peripheral wall of the planet shaft 13 having a
hollow center, a pair of bearing oil supply holes 81A and 81B are
formed at both ends, in the axial direction, of each rolling
surface 77. Specifically, the pair of bearing oil supply holes 81A
and 81B extend in the radial direction through the vicinity of the
base portions of the respective flanges 79. A recess 23a, which
communicates with the bearing oil supply holes 81A and 81B, is
formed at the outer circumferential face of the fixed support shaft
23. Space formed by the recess 23a and the inner circumferential
face 13a of the planet shaft 13 acts as oil reservoir space 83 for
storing the lubricating oil OL. The planet shaft 13 is provided
with a through-hole 85, which extends in the radial direction and
of which the position in the axial direction corresponds to that of
the front end of the recess 23a. Further, a bearing lubricating oil
guide path 87, which communicates with the through-hole 85, is
formed within the radially inner portion of the front plate 19. The
bearing lubricating oil guide path 87 of the front plate 19
communicates with an external lubricating oil source (not shown)
through the outer circumferential face of the cylindrical portion
19a, which is formed at the inner circumferential portion of the
front plate 19 and which protrudes frontward in the axial
direction.
[0047] The bearing lubricating oil guide path 87 of the front plate
19 (planet carrier 11), the through-hole 85 of the planet shaft 13,
the oil reservoir space 83, and the bearing oil supply holes 81A
and 81B of the planet shaft (inner ring) 13, which are formed as
described above, collectively serve as a bearing oil supply path LP
through which the lubricating oil OL is supplied to the rolling
elements 73 of the bearing 15. Through the bearing oil supply path
LP, the lubricating oil OL that is sent from the radially inner
side of the planet gear 7 is supplied to both ends of each rolling
element 73 which is a cylindrical roller.
[0048] As described above, the planet gear 7 is formed as a double
helical gear, which includes a pair of helical gears aligned in the
axial direction, and the annular groove 17 is formed between the
pair of helical gears. As shown in FIG. 8, multiple oil outlets 91
are formed at the annular groove 17 of the planet gear 7 as
through-holes extending in the radial direction. These oil outlets
91 are arranged at equal intervals in the circumferential
direction. The planet gear 7 rotates in a direction indicated by
arrow B, which is opposite to a direction in which one set of
helical teeth and the other set of helical teeth of the double
helical gear are inclined toward each other. Therefore, when the
lubricating oil OL is supplied to the gear tooth surfaces, the
lubricating oil OL flows into the annular groove 17 positioned at
the center of the planet gear 7.
[0049] Further, as shown in FIG. 9, the ring gear 9 is formed as a
double helical gear, which includes a pair of helical gears aligned
in the axial direction, and the annular groove 18 is formed between
the pair of helical gears. The ring gear 9 is divided in the axial
direction into two portions that are a gear half body 9a and a gear
half body 9b. Teeth formed on one of the gear half bodies are
inclined in a direction that is opposite to the inclination
direction of teeth formed on the other one of the gear half bodies.
Multiple outlets 93 are formed at the annular groove 18 of the ring
gear 9 as through-holes extending in the radial direction. The
outlets 93 are arranged at equal intervals in the circumferential
direction.
[0050] Next, the operation of the planetary gear system 1 according
to the above embodiment will be described.
[0051] The sun gear 5 of the planetary gear system 1 shown in FIG.
3 rotates in a direction indicated by arrow A. The driving force of
the rotation causes the planet gears 7 to rotate in a direction
indicated by arrow B, and also causes the planet gears 7 to revolve
in a direction indicated by arrow Rv together with the planet
carrier 11. The ring gear 9 rotates in a direction indicated by
arrow D.
[0052] The lubricating oil OL that is supplied from the outside and
that is guided into the baffle unit 35 through the gear lubricating
oil guide paths 53 (see FIG. 2) is jetted toward the forward mesh
position 43 through the oil supply holes 47 of the forward inclined
face 41b of the baffle unit 35 and toward the backward mesh
position 45 through the oil supply holes 47 of the backward
inclined face 41c of the baffle unit 35. The temperature at a
position where the teeth of gears come out of mesh becomes higher
than the temperature at a position where the teeth of gears come
into mesh. Therefore, for the purpose of cooling down such a
temperature-increased position, the amount of lubricating oil OL
supplied to the backward mesh position 45 where the teeth of the
gears come out of mesh is greater than the amount of lubricating
oil OL supplied to the forward mesh position 43. A part of the
lubricating oil OL jetted toward the backward mesh position 45
flows outward through the backward gap 39 between the backward side
face 37R of the baffle unit 35 and the backward planet gear 7R.
Most of the lubricating oil OL flowing through the backward gap 39
is collected into the baffle unit 35 through the backward
collection opening 55. In particular, the lubricating oil OL that
has been used for lubricating the backward planet gear 7R and the
sun gear 5 flows into the annular groove 17 shown in FIG. 8, owing
to the rotation of the planet gear 7 which is a double helical
gear. Then, the lubricating oil OL passes through the backward mesh
position 45 shown in FIG. 3 and flows into the collection guide
groove 57 of the baffle unit 35 (specifically, the central portion
57a shown in FIG. 5). Thereafter, the lubricating oil OL is
collected into the baffle unit 35 through the backward collection
opening 55. On the other hand, a part of the lubricating oil OL
that is jetted through the oil supply holes 47 toward the forward
mesh position 43 shown in FIG. 3 is collected into the baffle unit
35 through the forward collection opening 63.
[0053] The lubricating oil OL collected into the baffle unit 35
flows into the collection chamber 65. Thereafter, a part of the
lubricating oil OL is held back by the weir 69 and then supplied to
the ring gear 9 through the ring gear oil supply holes 59. In this
manner, the ring gear 9 is effectively lubricated. The lubricating
oil OL that overflows the weir 69 of the collection chamber 65 is
discharged through the axial directional outlet 67 to the outside
of the planetary gear system 1 in the frontward axial
direction.
[0054] As described above, the baffle unit 35 is provided between
the adjacent planet gears 7. The baffle unit 35 collects the
lubricating oil OL therein while preventing flows of the
lubricating oil around the respective adjacent planet gears 7 from
interfering with each other. This makes it possible to prevent a
large amount of lubricating oil OL from being adhered to the outer
periphery of the planet gears 7 over a long circumferential
distance. Accordingly, the agitation resistance of the lubricating
oil OL is reduced. As a result, power loss of the planetary gear
system 1 is reduced. It was confirmed through an experiment that
power loss was reduced by 34 percent as compared to conventional
art that does not include components corresponding to the
collection openings 55 and 63 of the baffle unit 35 and the oil
outlets 91 of the planet gear 7.
[0055] The lubricating oil OL that is supplied from the outside to
the rolling elements 73 of the bearing 15 through the bearing oil
supply path LP shown in FIG. 2 is, after lubricating the rolling
elements 73, discharged to the outside of the planet gear 7. Here,
the lubricating oil OL that is supplied to the rolling elements 73
through the bearing oil supple hole 81A which is disposed at an
outer position in the axial direction is, after lubricating the
rolling elements 73, discharged outward in the axial direction. On
the other hand, the lubricating oil OL that passes through the
bearing oil supply hole 81B which is disposed at an inner position
in the axial direction enters space 96 between the two rolling
element rows after lubricating the rolling elements 73. Then, at
each rolling element row, as indicated by arrows G, a part of the
lubricating oil OL passes between rolling elements 73 that are
adjacent to each other in the circumferential direction, and is
discharged outward in the axial direction. Another part of the
lubricating oil OL is discharged to the radially outer side through
the oil outlets 91. The lubricating oil OL that passes between
rolling elements 73 as indicated by arrows G increases the
agitation resistance for the rolling elements 73. However, by
forming the oil outlets 91, the amount of lubricating oil OL
passing between the rolling elements 73 is reduced. Accordingly,
the agitation resistance is reduced.
[0056] The lubricating oil OL that is supplied to the ring gear 9
through the ring gear oil supply holes 59 of the baffle unit 35 and
the oil outlets 91 of the planet gear 7 flows into the annular
groove 18 after lubricating the gear tooth surfaces of the ring
gear 9, and is then discharged in the radial direction to the
outside of the planetary gear system 1 from the outlets 93.
[0057] As described above, the oil outlets 91 are formed in the
planet gear 7 located at a radially outer position than the rolling
elements 73 which are supplied with the lubricating oil OL. This
makes it possible to efficiently discharge, to the outside of the
planet gear 7, the lubricating oil OL that is supplied to the
rolling elements 73 from the radially inner side. Accordingly, the
agitation resistance of the lubricating oil OL around the rolling
elements 73 is reduced. As a result, power loss of the planetary
gear system is reduced significantly. In addition, the lubricating
oil OL that is discharged from the planet gear 7 can be used for
lubricating the ring gear 9 which is disposed at a radially outer
position than the planet gear 7.
[0058] It should be noted that the structure of the planet gear 7,
in which the lubricating oil OL that has been supplied to the
bearing 15 is discharged to the radially outer side through the oil
outlets 91 which communicate with the space between the two rolling
element rows which are aligned in the axial direction, is
applicable not only to the above-described planetary gear system 1
but to any gear system, so long as the gear system includes a gear
that is rotatably supported by a fixed support shaft via a pair of
rolling element rows that are aligned in the axial direction.
[0059] Although a preferred embodiment of the present invention is
as described above with reference to the drawings, various
additions, modifications, and deletions may be made to the above
embodiment without departing from the spirit of the present
invention. Therefore, such additions, modifications, and deletions
also fall within the scope of the present invention.
INDUSTRIAL APPLICABILITY
[0060] According to the present invention, the lubricating oil that
is supplied to main rotating components of the planetary gear
system is efficiently discharged, and thereby power loss is
reduced. Thus, the present invention is useful to reduce power loss
in a planetary gear system.
REFERENCE SIGNS LIST
[0061] 1 planetary gear system [0062] 5 sun gear [0063] 7 planet
gear [0064] 9 ring gear [0065] 11 planet carrier [0066] 13 planet
shaft [0067] 17 annular groove of planet gear [0068] 35 baffle unit
[0069] 37F, 37R side face of baffle unit [0070] 41 tip portion of
baffle unit [0071] 43, 45 mesh position [0072] 47 oil supply hole
[0073] 55 collection opening [0074] OL lubricating oil
* * * * *